/* --- 1. 设计系统 (Design System) --- */
:root {
    --bg: #0a0a0a;
    --fg: #f5f5f7;
    --muted: #a1a1a6;
    --card: #111114;
    --accent: #2997ff;
    --border: rgba(255, 255, 255, 0.1);
    --maxw: 1100px;
}

@media (prefers-color-scheme: light) {
    :root {
        --bg: #fbfbfd;
        --fg: #1d1d1f;
        --muted: #6e6e73;
        --card: #ffffff;
        --border: rgba(0, 0, 0, 0.08);
    }
    .nav {
        background: rgba(251, 251, 253, 0.7);
        --border: rgba(0, 0, 0, 0.12);
    }
    .card {
        box-shadow: 0 4px 12px rgba(0,0,0,0.05);
    }
}


/* --- 2. 全局与基础样式 --- */
* { box-sizing: border-box; }
html, body { height: 100%; }
body {
    margin: 0;
    background: var(--bg);
    color: var(--fg);
    font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", Roboto, Helvetica, Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    -webkit-font-smoothing: antialiased;
    text-rendering: optimizeLegibility;
}

/* --- 3. 模块样式 (Components) --- */
/* --- style.css (仅展示需要替换的部分) --- */
/* --- style.css (更新后的导航栏部分) --- */

/* 顶部导航 */
.nav {
    position: sticky;
    top: 0;
    z-index: 10;
    width: 100%;
    /* 核心改动 1: 背景改为纯白 */
    background: #ffffff;
    /* 使用更明确的浅色边框 */
    border-bottom: 1px solid rgba(0, 0, 0, 0.08);
    transition: background .3s, border-color .3s;
    /* backdrop-filter 在纯色背景下无效，已移除 */
}

/* Logo 文字样式 */
.logo span {
    font-weight: 600;
    /* 核心改动 2: Logo 文字改为深色以保证可读性 */
    color: #1d1d1f;
    /* 移除了在浅色背景上不必要的阴影 */
    text-shadow: none;
}

/* 导航链接 */
.nav-links a {
    /* 核心改动 3: 默认颜色改为深灰色 */
    color: #6e6e73;
    text-decoration: none;
    font-size: 14px;
    transition: color 0.2s ease, transform 0.2s ease;
}

.nav-links a:hover {
    /* 核心改动 4: hover 时变为深黑色，并保留上浮效果 */
    color: #1d1d1f;
    transform: translateY(-1px);
}
.nav-inner { max-width: var(--maxw); margin: 0 auto; display: flex; align-items: center; gap: 16px; padding: 12px 20px; }
.logo { display: inline-flex; align-items: center; gap: 10px; text-decoration: none; color: var(--fg); }
.logo img {
    height: 28px; /* 您可以根据 Logo 的设计调整这个数值 */    width: auto;
}
.nav-links { margin-left: auto; display: flex; gap: 24px; }
.nav-links a { color: var(--muted); text-decoration: none; font-size: 14px; transition: color 0.2s ease; }
.nav-links a:hover { color: var(--fg); }

/* Hero 首屏 */
.hero { position: relative; overflow: hidden; padding: min(15vh, 140px) 20px 100px; text-align: center; }

/* 背景柔光渐变 (已更新) */
.glow{
    position: absolute;
    inset: -20% -20% auto;
    height: 60vh;
    pointer-events: none;
    filter: blur(80px);
    opacity: .35;
    background:
            radial-gradient(60% 60% at 30% 30%, #2997ff 0%, transparent 60%),
            radial-gradient(40% 40% at 70% 40%, #ff2d55 0%, transparent 60%),
            radial-gradient(40% 40% at 60% 80%, #ffd60a 0%, transparent 60%);
}

.hero-inner { max-width: var(--maxw); margin: 0 auto; position: relative; z-index: 1; } /* 添加 z-index 确保内容在 glow 之上 */
.eyebrow { font-size: 14px; letter-spacing: .12em; text-transform: uppercase; color: var(--muted); }
.title { font-size: clamp(42px, 6vw, 80px); line-height: 1.05; margin: 10px 0 18px; font-weight: 700; letter-spacing: -.02em; }
.subtitle { font-size: clamp(18px, 2.2vw, 22px); color: var(--muted); max-width: 720px; margin: 0 auto 32px; line-height: 1.6; }

/* 按钮 */
.cta { display: flex; justify-content: center; }
.btn { appearance: none; border: 0; padding: 14px 28px; border-radius: 999px; font-weight: 600; font-size: 16px; cursor: pointer; transition: .25s ease; }
.btn.primary { background: var(--accent); color: #fff; box-shadow: 0 0 0 0 rgba(41, 151, 255, 0.5); }
.btn.primary:hover { transform: translateY(-2px); box-shadow: 0 10px 25px -8px rgba(41, 151, 255, 0.4); }

/* 特性卡片 */
.grid { max-width: var(--maxw); margin: 60px auto; padding: 0 20px; display: grid; gap: 20px; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); }
.card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: 24px;
    padding: 28px;
    position: relative;
    overflow: hidden;
    transition: transform 0.2s ease, border-color 0.3s, box-shadow .3s;
    transform-style: preserve-3d;
}
.card h3 { margin: 0 0 8px; font-size: 22px; }
.card p { margin: 0; color: var(--muted); line-height: 1.6; }
.card .chip { position: absolute; top: 18px; right: 18px; padding: 6px 12px; border-radius: 999px; font-size: 12px; font-weight: 500; color: var(--fg); background: rgba(255, 255, 255, 0.05); }

/* 页脚 */
footer { color: var(--muted); border-top: 1px solid var(--border); margin-top: 80px; }
.foot-inner { max-width: var(--maxw); margin: 0 auto; padding: 32px 20px; display: flex; gap: 16px; align-items: center; justify-content: space-between; flex-wrap: wrap; }
.foot-links { display: flex; gap: 20px; }
.foot-links a { color: var(--muted); text-decoration: none; font-size: 14px; transition: color 0.2s ease; }
.foot-links a:hover { color: var(--fg); }

/* 入场动画 */
.reveal { opacity: 0; transform: translateY(16px); transition: 0.8s cubic-bezier(0.2, 0.8, 0.2, 1); }
.reveal.visible { opacity: 1; transform: none; }

/* --- 1. 设计系统 (Design System) --- */
:root { /* ... */ }
@media (prefers-color-scheme: light) { /* ... */ }

/* --- 2. 全局与基础样式 --- */
* { box-sizing: border-box; }
html, body { height: 100%; }
body {
    margin: 0;
    background: var(--bg);
    color: var(--fg);
    font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", Roboto, Helvetica, Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    -webkit-font-smoothing: antialiased;
    text-rendering: optimizeLegibility;
    transition: overflow 0.3s ease; /* 防止滚动条闪烁 */
}
body.modal-open {
    overflow: hidden; /* 模态窗口打开时禁止背景滚动 */
}

/* --- 3. 模块样式 (Components) --- */
/* .nav, .hero, .card 等样式保持不变 */
/* ... */

/* --- 4. 新增：认证模态窗口 (Auth Modal) --- */
.auth-modal {
    display: none; /* 默认隐藏 */
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(0, 0, 0, 0.6);
    backdrop-filter: blur(5px);
    justify-content: center;
    align-items: center;
    opacity: 0;
    transition: opacity 0.3s ease;
}
.auth-modal.visible {
    opacity: 1;
}

.modal-content {
    background-color: var(--card);
    margin: auto;
    padding: 32px;
    border: 1px solid var(--border);
    border-radius: 24px;
    width: 90%;
    max-width: 400px;
    position: relative;
    box-shadow: 0 15px 35px rgba(0,0,0,0.25);
    transform: scale(0.95);
    transition: transform 0.3s ease;
}
.auth-modal.visible .modal-content {
    transform: scale(1);
}

.close-btn {
    color: var(--muted);
    position: absolute;
    top: 15px;
    right: 20px;
    font-size: 28px;
    font-weight: bold;
    cursor: pointer;
    transition: color 0.2s ease;
}
.close-btn:hover, .close-btn:focus {
    color: var(--fg);
}

.auth-tabs {
    display: flex;
    margin-bottom: 24px;
    border-bottom: 1px solid var(--border);
}
.tab-link {
    flex: 1;
    padding: 12px;
    background: none;
    border: none;
    color: var(--muted);
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    border-bottom: 3px solid transparent;
    transition: color 0.2s, border-color 0.2s;
}
.tab-link:hover {
    color: var(--fg);
}
.tab-link.active {
    color: var(--fg);
    border-bottom-color: var(--accent);
}

#auth-form .form-group {
    margin-bottom: 16px;
}
#auth-form label {
    display: block;
    margin-bottom: 6px;
    font-size: 14px;
    font-weight: 500;
    color: var(--muted);
}
#auth-form input {
    width: 100%;
    padding: 12px;
    background-color: rgba(0,0,0,0.2);
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--fg);
    font-size: 16px;
    transition: border-color 0.2s, box-shadow 0.2s;
}
#auth-form input:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(41, 151, 255, 0.3);
}
@media (prefers-color-scheme: light) {
    #auth-form input { background-color: rgba(0,0,0,0.05); }
}

#auth-form .btn-submit {
    width: 100%;
    margin-top: 8px;
}

.switcher-text {
    text-align: center;
    font-size: 14px;
    color: var(--muted);
    margin-top: 20px;
}
.switcher-link {
    color: var(--accent);
    font-weight: 500;
    text-decoration: none;
}
.switcher-link:hover {
    text-decoration: underline;
}
/* --- 追加的样式：用于动态页签切换 --- */

/* 页签按钮容器 */
.tabs-container {
    display: flex;
    justify-content: center;
    gap: 16px;
    margin-bottom: 40px;
}

/* 页签按钮样式 */
.tab-btn {
    appearance: none;
    background: transparent;
    border: 1px solid var(--border);
    color: var(--muted);
    padding: 10px 24px;
    border-radius: 999px;
    font-size: 16px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.25s ease;
}

/* 鼠标悬浮效果 */
.tab-btn:hover {
    color: var(--fg);
    border-color: var(--accent);
}

/* 激活状态的按钮样式 */
.tab-btn.active {
    background: var(--accent);
    color: #fff;
    border-color: var(--accent);
}

/* 控制非激活内容区域的隐藏 */
.feature-set {
    display: none; /* 默认隐藏 */
    animation: fadeIn 0.6s ease; /* 添加一个简单的淡入动画 */
}

/* 控制激活内容区域的显示 (它本身已有 .grid 样式) */
.feature-set.active {
    display: grid; /* 当被激活时，使用 grid 布局显示 */
}

/* 淡入动画定义 */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}